arch/x86/lib/usercopy_64.c: fix __copy_user_flushcache() cache writeback

If we copy less than 8 bytes and if the destination crosses a cache
line, __copy_user_flushcache would invalidate only the first cache line.

This patch makes it invalidate the second cache line as well.

Fixes: 0aed55a ("x86, uaccess: introduce copy_from_iter_flushcache for pmem / cache-bypass operations")
Signed-off-by: Mikulas Patocka <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Reviewed-by: Dan Williams <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Jeff Moyer <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Toshi Kani <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Ross Zwisler <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: <[email protected]>
Link: https://lkml.kernel.org/r/alpine.LRH.2.02.2009161451140.21915@file01.intranet.prod.int.rdu2.redhat.com
Signed-off-by: Linus Torvalds <[email protected]>

Author: Mikulas Patocka

arch/x86/lib/usercopy_64.c

@@ -120,7 +120,7 @@ long __copy_user_flushcache(void *dst, const void __user *src, unsigned size)
 	 */
 	if (size < 8) {
 		if (!IS_ALIGNED(dest, 4) || size != 4)
-			clean_cache_range(dst, 1);
+			clean_cache_range(dst, size);
 	} else {
 		if (!IS_ALIGNED(dest, 8)) {
 			dest = ALIGN(dest, boot_cpu_data.x86_clflush_size);